A method for soldering a component on a holder by addition of mass forming solder, of the type comprising a step in which the mass is heated is already known in the state of the art. In a conventional manner, the mass forming solder consists of a soldering paste or a thin strip cut up into discs or rectangles which is inserted between the semi-conductor chip, and the holder. Generally, before the heating step, the component is placed precisely on the mass forming solder in an initial position guaranteeing parallelism between the chip and the holder.
When the mass forming solder is heated to a temperature greater than or equal to the melting point of the solder, the mass melts and on solidifying assembles the chip to the holder. For example, to heat the solder, a laser beam is directed to a first side of the holder opposite a second side of the holder bearing the mass, at the position of this mass, and the heat generated by the impact of the beam on the holder propagates through the holder to the mass.
Generally, the contact surfaces between the mass forming solder and the chip, firstly, and the holder and the mass forming solder, secondly, are relatively irregular making heat transfer from the holder to the chip difficult during the heating step.
Consequently, generally, to improve the heat transfer between the chip and the holder, while positioning the chip before the heating step a compression force is applied on the assembly comprising the chip, the mass forming solder and the holder to remove, as much as possible, the surface irregularities.
The intensity of this compressive force must be relatively low to avoid damaging the semi-conductor chip during compression.
Since the intensity of this compressive force is relatively low, however, some irregularities remain making the heat transfer sometimes insufficient during the heating step.
Consequently, the temperature of the assembly comprising the chip, the mass and the holder is not homogeneous during the heating step and the joint resulting from cooling of the mass forming solder may then exhibit faults, such as in particular non uniform thickness.